The invention relates generally to a device for controlling the exhaust emissions produced by an internal-combustion engine and, more particularly, to a device of the type comprising a soot filter arranged in an exhaust-gas system. In such a device, the soot filter is made of a flexible filter band which is traversed by the flow of the exhaust gas in a first zone and which can be advanced forward. The filter band may be advanced, either continuously or intermittently, by means of a drive mechanism.
A related device for controlling exhaust emission is disclosed in the German Published Patent Application 38 37 669. It describes a soot filter installation for diesel engine exhaust gases having a filter band made of organic or inorganic material in the form of bonded fiber-fabric bands. These bands are designed to filter soot and other contaminant particles out of the traversing exhaust gas. In this device, the filter band is wound, loaded with contaminants, onto a spool and is fed to an external waste disposal unit. However, it is very costly and complicated, not to mention not very economical, to dispose of contaminant particles and the filter band externally. The exhaust gases, which form when the filter band and the particles are disposed of externally, must be filtered once more, thus requiring additional expenditure of time and energy. Moreover, the working properties of this soot filter installation for diesel engines are not very satisfactory, since high temperatures and pressures act directly on the filter band. The operational costs entailed in developing a functional filter material are extremely high and, due to the arrangement, introduce troublesome inaccuracies in controlling the band. Thus, one of the of a more economical exhaust emission device of the general type discussed above that is both economical and efficacious, and which does not rely on such multiple steps for the elimination of pollutants.
There remains a need for a device lacking the aforementioned deficiencies that is cost-effective, and that takes up a minimal amount of space. In such a system, both the filter band and the particles should be disposed of in the filtering system itself; the system should also have good working properties during normal operational use.